Floor plan of a single-family house with approximately 150 sqm on a rear lot

Here is the aerial photograph.
A house is currently being built in the north. It is located in the northeast of parcel number 173/5. Moving the house to the east may possibly mean even higher development costs; it might then require a manhole/lift system, etc.
The gravel path cannot be used as an access road; the houses in the north probably still have some kind of grandfather rights or similar.

Shifting the house to the east means potentially even higher development costs, possibly requiring an inspection shaft/lifting system, etc.

Under the condition that the house should be as far west as possible, I would orient my "living spaces" such as living room / terrace etc. rather towards the southeast. The access remains difficult if a turning option on your property is a requirement. But the next neighbor to the north manages that as well ;-) . It seems you have oriented yourselves quite a bit according to him, right? The houses to the north are by the way pretty much aligned with their east side and quite close to the (east) property boundary. This could possibly be a kind of building line that you would have to comply with according to §34. It would now be interesting where exactly the house directly north of you stands. If that is the case, the room layout should be different than if you can build as far west as possible (i.e. 3m next to the neighbor's boundary). I would clarify something like that before investing too much detail and "infatuation" in a floor plan.

No, his garage doors are supposed to face west.

I don’t understand that. How does he want to get to the garages from the west past his existing house? And then you also mention an entrance platform of his on the north directly on the street. I can't see that. Where is my flaw in reasoning?

I don't understand that. How does he want to get to the garages from the west past his existing house? And then you also mention an entrance platform of his on the north side directly at the street. I can't see that. Where is my mistake in thinking?

That's how I currently understand it (although the neighbor's driveway past the house is not 3m wide):

Is that correct ?

Exactly, here with the entrance base.

Just a thought: if the neighbor constantly uses your driveway, does he also help repair it when it breaks?

Do you already have a company you want to build with or are you planning to start first to get a feel for the property?
Can you also provide the dimensions of the property (the entire rectangle is sufficient, without the driveway)?